PURPOSE: To reduce cutting resistance of a material, and cut it smoothly and properly by small motive power by cutting the material deep by a cutting edge, rotating the material by a constant angle by an index device, and repeating these works successively after the material is cut deep by the cutting edge.

CONSTITUTION: When a material 3 is cut, first of all, the material 3 is supported with a material support part 1 by a chuck 4 through an index device 2. Next, a cutting edge 5 is moved rectilinearly, and the material 3 is cut into up to a prescribed depth. In succession, after the material 3 is rotated by a constant angle by the index device 2, the material 3 is cut into up to a prescribed depth by the cutting edge 5. Afterwards, similar work is repeated successively, the material 3 is cut completely. Thereby, since resistance is reduced when the material 3 is cut, the material 3 can be cut smoothly and properly by small motive power.